Pig Butchering scams typically would rely on an app for the the “investing” portion of the scam. They use apps that are in the google play store, because that comes with a belief of some level of (completely false) security and legitimacy for people that don’t know better which makes people more likely to believe it is a real investing app and not a trap.

Edit: I’m not aware of any of them trying to get people to side-load apps. The average scammer is likely not able to go through the hoops required to get a random person to successfully side-load an app on Android… I am fully against this move from google on all levels, the idea that it is for security is a blatant lie. Google is doing this for control over our devices. Android, by default, blocks side-loading already without going deep into settings to enable “install unknown apps”.